One more quick question.

1975 F250 360 RWD auto.

When we checked and figured out some of the vacuum mess under the hood? I noted the spark delay valve was missing in action....totally El' Goneo!

The parts houses list several depending on color code--which we of course do not have.

Any suggestions are helpfull...I can 'guess'...but I'd like things to run correctly when we are done LOL.

S-

 

Do you need one to pass emissions? If you don't, and your truck runs good, I would leave it out. Mil1lion(or numberdummy) will be able to help you out if you can get your calibration code off of the valve cover sticker, not the one on the side with the words you can understand, but the one on the front, with a series of numbers and letters on it. Find it, take a picture so Dennis wont have to guess.

 

Ditch all the smog junk it will run a lot better.

you only need to keep the following

PCV
Vacuum advance (run straight to metered vacuum port)
Brake booster
transmisson modulator valve (run to full manifold vacuum)

 

Thankfully this truck is over the emission date limit for the state. We've been weeding out a lot of the broken/busted up vacuum lines already. Heck, behind me in my office I even have a new brake booster vacuum line with the check valve ready to go in on Sunday. (found a lot of cracks in ours. Kinda funny...guy ask why I wanted to replace the check valve considering it still works? My reply? "Ever try to get a thick rubber hose off a 30+ year cheapo bit of plastic?)

If it's not something that will hose up the truck? Probably will leave it off then.

Thanks again!!

S-

 

D3FZ-12A091-A .. Spark Delay Valve ~ Black 'n White.

 

LOL...Bill to the Rescue!!!!!!!!

I found so many of the flippen things listed it was like I was pulling my hair out. And the people that do carry them? First question--what is the color code? Hard to do when the vacuum line was run directly to the carb--and the one it had? Probably sitting in a field somewhere.... All this fun for vacuum advance. Next question would be---what in the heck does it do, and is it important? LOL

Thanks again Bill!

S-

 

the vacuum advance, it advances your timing as the engine speeds up. Say for instance, your initial timing is at 8*. For an engine at idle, that is plenty of time for the spark to ignite the fuel. As the engine speeds up, there needs to be a fraction of a second sooner ignition to get the same result (the piston is moving faster, but the explosion still takes the same amount of time) The timing is advanced gradually to make up for that. At Full Tilt Boogie, the advance is retarded to help provent detonation. To tell if your vacuum advance still works, unplug it at the distributor, hook up a new hose to it, suck on the other end. If your rotor moves, the diaphram works. In most cases, the vacuum source is ported manifold vacuum, meaning the vacuum signal gets stronger the faster the engine spins. Vacuum advance is important to fuel economy and power. You can get away without using it, the distributor has mechanical advance built into it, but I would rather use it than not.

 

Specifically, the mechanical advance should advance the timing in relation to engine speed (i.e, rpm). The vacuum advance canister advances/retards the timing in relation to engine load (i.e, the higher the load = the less vacuum = less timing advance, while the lower the load = more vacuum = more timing advance. When under light load the fuel mixture is less dense and takes longer for the combustion process to complete, therefore the timing needs to be advanced so that the combustion pressure peaks about 12 degrees past TDC.)

The mechanical advance and the vacuum advance are independant of each other. The mechanical advance will advance the distributor rotor in relation to the distributor shaft, while the vacuum advance will rotate the breaker plate in relation to the rotor.

The Spark Delay Valve contains a very small orifice so that if you suddenly lift your foot when under a heavy load, the sudden high vacuum will take roughly 1.5 seconds to get to the vacuum advance can. This will keep the engine from surging from a sudden vacuum timing advance just when you wanted to back off.

On many Ford advance cans you can remove the vacuum hose and insert an allen wrench in the nipple and engage the adjustment bolt and adjust the resistance of the diaphram spring to tailor the amount of advance for a given amount of vacuum.

 

That's pretty much what I figured. I know the operation of vacuum advance, but hadn't much idea why Ford used delay valves on several items. Heck, the EGR system also has one floating off in the breeze. Until I get the spacer plate replaced? That's exactly where it's gonna stay. LOL

It makes sense to delay that vacuum 'hit' to the advance while doing rapid decel. I'll add it to my rockauto list. (those guys are gonna love me this year LOL)

S-

 

This sounds like it'd even be useful on a performance orientated engine..

Why do people remove them? (mildly old post, but, related)

 

I would venture a guess that stuff that is helpful is removed because people are either not educated enough to keep it working properly, don't know how to put it back together correctly, are too lazy to fix it, think it hurts power, or do not like the looks of the extra clutter on the engine.

 

Hard to answer. Clutter? Ehhhh...If that's the excuse it's a weak one. There is already a vacuum hose there, and this thing looks like maybe 5 quarters stacked on top of each other.

I got lucky and found a 'NOS' one on Epay...err...Ebay. The next question would be regarding a 'check valve' that I've also seen in use. Gots the spark delay one, but unsure about the vacuum check valve.

(ebay seller was actually about 5 bucks cheaper then purchasing a new one from the online stores--so I'm not complaining)

S-

 

You guys can find stuff like this in my automotive section of my photobucket page.

 

I'm actually going to work on a sort of 'universal' vacuum diagram.

I suspect some of this stuff might be useful, if only people knew how to hook it up.
-The ported vacuum switch that gives the distributor full vacuum when the temp goes over 245 degrees seems useful.
-charcoal vapor can hookup
- The vacuum setup for the air cleaner. Some seem to have a check valve, while others do not.
- The spark delay valves

Anyone ever try to come up with something like this before, from a performance standpoint? Some charcoal boxes have 2 some 4 ports. I wonder which is easier/best used from a pure performance (I don't want gas stink) standpoint, regardless of original application.

Lots of the performance EGRs don't have a provision for an EGR, it seems any vacuum diagram I find, has an EGR and I'm not sure how it'd be removed.

 

I don't have an EGR on my 429